Corrosion-proofing composition including phosphate esters



United States Patent 3,287,178 CORROSION-PROOFING COMPOSITION INCLUDING PHOSPHATE ESTERS Robert G. Wurstner, Richmond Heights, Ohio, assignor to The Lubrizol Corporation, Wicklifie, Ohio, a corporation of Ohio No Drawing. Filed May 23, 1963, Ser. No. 282,560 12 Claims. (Cl. 148-616) The present invention relates, as indicated, to a corrosion-proofing composition, which composition is adapted to form a protective coating on metal articles. In a more particular sense, it relates to a method for protecting metal articles, especially ferrous metal articles, against corrosion.

The corrosion of metal articles is of obvious economic significance in many industrial applications and, as a consequence, the inhibition of such corrosion is a matter of prime consideration. It is particularly significant to users of steel and other ferrous alloys. The corrosion of such ferrous metal alloys is largely a matter of rust formation, which in turn involves the overall conversion of the free metal to its oxides.

The theory which best explains such oxidation of ferrous metal surfaces postulates the essential presence of both water and oxygen. Even minute traces of moisture are suflicient, according to this theory, to induce the dissolution of iron therein and the formation of ferrous hydroxide until the water becomes saturated with ferrous ions. The pressure of oxygen causes oxidation of the resulting ferrous hydroxide to ferric hydroxide, which then settles out of solution and is ultimately converted to ferric oxide or rust.

The above sequence of reactions'can be prevented, or at least in large measure inhibited, by relatively impermeable coating which has the efiect of exculding moisture and/ or oxygen from contact with the metal surface. Such coatings are often exposed to high humidity, corrosive atmospheres, etc., and to the extent that these coatings are penetrated or otherwise harmed by such influences they become ineffective from the desired purpose. It is also important that such coatings adhere tightly to the metal surface and resist flaking, blistering, and other forms of loss of adhesion. A satisfactory corrosionproofing coating, then, must have the ability to resist weathering, high humidity, and corrosive atmospheres such as salt-laden mists or fogs, air contaminated with industrial waste, etc., so that a uniform protective film is maintained upon all or most of the metal surface.

Various derivatives of acid esters of phosphoric or phosphorothioic acids have been investigated by Workers engaged in the task of providing protective coatings for metals. In US. Patent 2,080,299, for example, Benning et a1. propose the treatment of ferrous metal with phosphate acid esters and their alkali metal or ammonium salts to prevent rusting. Somewhat similarly, Butler and Le Suer (US. Patents 2,861,907 and 2,820,723) find that salt-esters of complex phosphorothioic acids are effective in preventing or retarding the corrosion of metals. Although such known derivatives have provided means for combating the corrosion of metals, they have not been completely satisfactory because of certain inherent shortcomings. The simple salt-esters of phosphoric acid are readily Washed or abraded from a metal surface and thus provide complete protection only in a favorable environment. The salt-esters of phosphorothioic acids, on the other hand, have the disadvantage, under certain conditions, of developing an objectionable odor reminiscent of hydrogen sulfide, particularly when a film of such a salt-ester come in contact with water or humid atmospheres.

It is, therefore, a principal object of the present invention to provide a novel, liquid corrosion-proofing composition.

Another object is to provide a method for inhibiting the corrosion of metal articles, especially ferrous metal articles.

A further object is to improve the adhesion of known, siccative organic coating compositions to metal articles.

A still further object is to improve the corrosion-proof- 1 ing characteristics of known, siccative organic compositions.

These and other objects of the invention are realized by the provision of a liquid corrosion-proofing composition adapted to form a protective coating on metal articles which comprises the combination of (A) the product obtained by mixing one mole of at least one aliphatic amine containing at least about 6 carbon atoms with from about 0.25 to about 2 moles of aqueous chromic acid and heating the mixture to remove substantially all water present, and

(B) a mixture of phosphate esters prepared by the process which comprises the reaction of:

(a) one mole of a phosphorous-containing reagent selected from the group consisting of phosphorous pentoxide and phosphoric acids with (b) from about 1 to about 10 moles of an alkylphe- 1101 at a temperature of at least about 40 C.

In most instances, the corrosion-proofing composition of this invention will comprise from about 0.05 to about 20 parts by weight of A per part of B.

The corrosion-proofing compositions of this invention are useful principally as ingredients in known, siccative organic coating compositions such as solvent-based paints, varnishes, lacquers, primers, synthetic resins, and enamels, to which compositions they impart enhanced corrosioninhibiting characteristics. The siccative organic coating composition may also be an aqueous base or emulsion paint such as synthetic latex paints derived from acrylic resins, polyvinyl alcohol resins, alkyd resins, etc., by emulsification thereof with water, as well as water soluble paints derived from water-soluble alkyl resins, acrylic resins, and the like. Such siccative organic coating compositions may also contain conventional improving agents such as pigment extenders, anti-skinning agents, driers, gloss agents, color stabilizers, etc. When used for this purpose, i.e., to improve known coating compositions, a minor proportion, generally from about 0.1 to about 25%, of the corrosion-proofing composition of this invention is blended with a major proportion, generally from about 99.9 to about 75% of a siccative organic coating composition, all parts being by weight.

Thin films of the corrosion-proofing composition per se of the present invention are also effective in protecting metal articles, especially ferrous metal articles, against the ravages of corrosion. If desired, a topcoat of a known siccative organic composition may be subsequently applied so as to provide additional protection, decorative effects, etc.

COMPONENT A This component, as indicated, is prepared by mixing one mole of at least one aliphatic amine containing at least about 6 carbon atoms with from about 0.25 to about 2 moles of aqueous chromic acid and heating the mixture to remove substantially all water present. The

amine and the aqueous chromic acid within the range from the stoichiometric amounts or the amine acid chromate (equimolar proportions of the amine and aqueous chromic acid) to the stoichiometr-ic amounts for the normal amine chromate (one mole of the amine and 0.5 mole of aqueous chromic acid). It is also desirable in some instances to use two or more products derived from reaction involving different amounts of the amine and the aqueous chromic acid. Of course, proportions of the amine and aqueous chromic acid outside the scope of the broad range of 1 mole of the amine and from about 0.25 to about 2 moles of aqueous chromic acid may be employed, if desired, although the products of such reaction will contain excess amine or excess chromic acid and are, therefore, uneconomical and not preferred for the purposes of this invention. Amines useful for the preparation of Component A include any of the various aliphatic primary, secondary, and tertiary m-onoamines and polyamines containing a total of from about 6 to about 30 or more carbon atoms, which amines may also contain substituents such as chloro, fiuoro, bromo, nitro, nitroso, ether, ester, sulfide, etc. Examples of such amines include triethylamine, di-n-butylamine, di-isobutylamine, triisobutylamine, 6-chloro-n-hexylamine, 3-amino-n-heptane, 2-ethylhexylamine, tertiary-octyl primary amine, 3,5,5- trimethyl-hexylamine, n-decylamine, di-n-decylamine, trin-decylamine, tertiary-dodecyl primary amine, tertiaryoctadecyl primary amine, cetylamine, n-oct-adecylamine,

eicosylamine, docosylamine, hexacosylamine, triacontylamine, hexatriacontylamine, triethylenetetramine, tetraethylenepentamine, pentaethylenehexamine, dicyclohexylamine, isooctenylamine, methylcyclohexylamine, di-isooctenylamine, 2-butoxy-ethylamine, aminoet-hyl oleate, aminopropyl stearate, bis-(dimethylaminopropyl)amine, n-aminopropyl-octadecylamine, aminomenthane, etc. From the foregoing, it will also be noted that the aliphatic radicals may possess a cyclic or acyclic structure.

A particular preference is expressed for monoalkyl primary amines conforming to the structure RNH where R is an alkyl radical. Examples of such monoalkyl primary amines include n-hexylamine, Z-ethylhexylamine,

laurylamine, cetylamine, and tertiary-alkyl primary amines. The tertiary-alkyl primary amines referred to conform to the characterizing structure i C-(|1NH2 wherein a tertiary carbon atom, i.e., one devoid of hydrogen atoms, is bonded to a primary amino radical, i.e., -NH Such tertiary-alkyl primary amines should con tain at least about 6 and generally not more than about 30 carbon atoms in the tertiary-alkyl substituent. In most instances, the tertiary-alkyl substituent will contain from about 10 to about 24 carbon atoms. Specific examples of tertiary-alkyl primary amines useful for the purposes of this invention include tertiary-octyl primary amine, tertiary-decyl primary amine, tertiary-dodecyl primary amine, tertiary-tetradecyl primary amine, tertiary-hexadecyl primary amine, tertiary-heptadecyl primary amine, tertiary-octadecyl primary amine, tertiary-eicosyl primary amine, tertiary-docosyl primary amine, tertiary-tetracosyl primary amine, tertiary-triacontyl primary amine, etc. It is not necessary'to use a single tertiary-alkyl primary amine. In fact, it is generally more convenient to use a mixture of such amines wherein the tertiary-alkyl substituents present contain from about 10 to about 24 carbon atoms. A typical available mixture of such tertiaryalkyl primary amines, for example, consists of tertiaryalkyl primary amines containing from about 12 to about 15 carbon atoms, said mixture averaging about 12 carbon atoms per amine molecule. The mixture contains about 85% of tertiary-dodecyl primary amine, about 10% of tertiary-pentadecyl amine, and less than about of acid solution over a period of 0.5 hour.

reaction carries the temperature from 25 C. to about amines having less than 12 or more than 15 carbon atoms. Another available mixture of tertiary-alkyl primary amines suitable for the purposes of the present invention consists of tertiary-alkyl primary amines having from about 18 to about 24 carbon atoms and averaging about 20 carbon atoms per amine molecule. This mixture of tertiary-alkyl primary amines contains about 40% of tertiary-octadecyl primary amine, about 30% of ter- 1 tiary-eicosyl primary amine, about 15% of tertiary-docosyl primary amine, about 10% of tertiary-tetracosyl amine, and about 5% of amines outside the C to C mixtures may be prepared from polypropylene or polybutene fractions or mixtures thereof. Thus, a selected polymer fraction composed of mixed polyolefins within the desired molecular Weight range can be converted to the corresponding tertiary-alkyl primary amines. as follows. The selected polyolefin fraction is first hydrated by means of sulfuric acid and water to convert it to the corresponding alcohols. The alcohol mixture is then converted to an alkyl chloride by the reaction with dry hydrogen chloride. Finally, the alkyl chloride mixture is condensed under pressure with ammonia to yield the deslred tertiary-alkyl primary amine mixture. Specific methods of preparing tertiary-alkyl primary amines are described in the Journal of Organic Chemistry, volume 20 (1955), beginning at page 295.

The aqueous chromic acid employed in the prepara-.

reactants be reacted under conditions such that substan-,

tially all of the water present will be removed. Thus, for example, the reactants may be maintained at the boiling point until water ceases to distill from the reaction mass. A more rapid and economical removal of water may be effected by heating the reaction mass at a temperature of, 1

say, 60 100 C. under reduced pressure until no more water distills. In any event, the process is carried out until water no longer distills from the reaction vessel.

If desired, the somewhat viscous product may be diluted with a solvent such as benzene, toluene, xylene, aromatic petroleum spirits, naphtha, chlorobenzene, trichloroethylene, tetrachloroethylene, etc., to facilitate handling.

The following examples are submitted to illustrated specific modes of preparing Component A. They are presented for purposes of illustration only and are not to be construed as limiting the scope of the present invention, except as the latter is defined by the appended.

claims.

Example 1 122 parts of Water and 162 parts of CrO- are mixed at 25-40 C. to yield a concentrated aqueous solution of chromic acid. 620 parts of a mixture of C -C tertiary alkyl primary amines (2 moles of amine permole of aqueous chromic acid) is added to the aqueous chromic An exothermic C. The whole is then stirred for about 2 hours at 80-100 C. and then the pressure is reduced to about 50 mm. Hg to remove substantially all of the water present. 47 parts of organic distillate is separated from the aqueous distillate and recharged to the reaction vessel. To facilitate handling the somewhat viscous product.

parts of aromatic petroleum spirits is added. The product a 90% solution of the active chemical in aromatic petroleum spirits, shows the following analyses.

Percent Chromium 9.5 Nitrogen 5. 1

Example 2 Percent Chromium 12.6 Nitrogen 4.5

Example 3 200 grams of CrO is mixed with 200 grams of water to form a concentrated aqueous solution of chromic acid. Such solution is then added to 764 grams of a mixture of Gig-C15 tertiary-alkyl primary amines (2 moles of amine per mole of aqueous chromic acid) over a period of 0.7 hour. An exothermic reaction causes the temperature to rise to about 37 C. One liter of benzene solvent is added to the reaction vessel and the contents refluxed using a sidearm water trap to remove water. After substantially all of the water is removed, the benzene solvent is removed at 87 C./50 mm. Hg. The product, a brown viscous liquid, shows the following analyses.

'Percent Chromium 1 1.0 Nitrogen 5.7

Example 4 Percent Chromium 17.1 Nitrogen 4.46

Example 5 In the same manner set forth in Example 3, 200 grams of concentrated aqueous chromic acid (from 100 grams each of CrO and water) and 573 grams of mixture of C -C tertiary-alkyl primary amines (3 moles of the amine per mole of aqueous chromic acid) are processed to yield a product useful for the purposes of this invention. The product, a clear brown viscous liquid, shows the following analyses.

Percent Chromium 7.40 Nitrogen 6.1 1

Example 6 A product is prepared in the same manner set forth in Example 3, except that 596 grams of a mixture of C -C tertiary-alkyl primary amines averaging about 20 carbon atoms per molecule is employed as the amine reactant.

Example 7 387 grams of CrO is mixed with 244 grams of water to form a concentrated aqueous solution of chromic acid. Such solution is added to 1000 grams of Z-ethylhexylamine (2 moles of amine per mole of aqueous chromic acid) over a period of 1.75 hours at 25-96 C., the temperature rising as indicated due to the exothermic nature of the reaction. After all of the aqueous chromic acid hasbeen added, the whole is stripped under a nitrogen atmosphere at 76 C./ 110 mm. Hg to remove substantially all the water present. The product, a brown liquid, shows the following analyses.

Percent Chromium 14.56 Nitrogen 6.23

COMPONENT B where x is 1 or 2 and R is the organic radical of the alkylphenol employed, although some neutral triesters of the formula may also be formed. The stoichiometry of the reaction is likewise not clear, for a complex mixture of esters always results regardless of the relative proportions of the alkylphenol and the phosphorus-containing reagent. In any event, from about 1 to about 10 and more often from about 2 to about 6 equivalents of alkylphenol are employed per mole of phosphorus-containing reagent. The term equivalen as used herein is employed in its usual chemical sense, i.e., an equivalent of an alkyl monohydric phenol is one mole thereof, an equivalent of an alkyl dihydric phenol is two equivalents thereof, etc. For the purposes of the present invention, it is generally preferred to employ from about 3 to about 5 equivalents of alkylphenol per mole of the phosphorus-containing reagent.

The reaction conditions are not critical. It generally suffices to heat the alkylphenol and the phosphorus-containing reagent ata temperature ranging from about 40 C. to a point just below the decomposition pointof the reaction mixture. Ordinarily, the reaction is carried out within the temperature range of from about 50 C. to about 300 C. for 0.1 to 30 hours or more. The lower temperatures, as expected, necessitate longer reaction periods. When phosphoric acid rather than phosphorus pentoxide is used as the phosphorus-containing reagent, it is best to employ temperatures above C. so as to insure the removal of water. In some cases, it is desirable to carry out the reaction in an inert solvent such as benzene, xylene, toluene, rnesi-tylene, cyclohexane, aromatic petroleum spirits, chlorobenzene, trichloroethylene, tetrachloroethylene, turpentine, di-isopropyl ether, etc. The solvent may be removed after the reaction is completed or it may be allowed to remain as a diluent.

The phosphorus-containing reagent, as indicated, is selected from the group consisting of phosphorus pentoxide and phosphoric acids. For reasons of convenience, economy and reactivity in preparing the mixture of phosphate esters, phosphorus pentoxide is generally preferred. Where it is desired to employ a phosphoric acid, .any of the several available phosphoric acids such as polyphosphoric, orthophosphoric, metaphosphoric, or pyrophosphoric acid, may be used either alone or in admixture as this reagent. It is also feasible to use mixtures of phosphorus pentoxide with one or more of such phosphoric acids. Phosphoric acids, if employed, will generally be the ordinary commercial 85% or 100% orthophosphoric acid, although more dilute acids containing at least about 25% H PO are also usable.

The alkylphenol may be a mono-alkyl or poly-alkyl monohydric or polyhydric phenol. The alkyl groups may be of any size, ranging from methyl up to alkyl groups derived from olefin polymers having molecular weights as high as 50,000 or more, and may contain olefinic linkages. The alkyl group may also have a cyclic structure, if desired. Preferably the alkylphenol is a mono-alkylphenol in which the alkyl group is acyclic and contains from 1 to about 30 carbon atoms, preferably at leastabout 4 carbon atoms. Typical examples of useful alkylphenols include, e.g., ortho, meta, and para-cresols; ortho, meta, and paraethylphenols; para-isopropylphenol, para-allylphenol, para-tertiary butylphenol, ortho-n-amylphenol,

para-tertiary amylphenol, n-hexylphenol, cyclohexylphenol, methylcyclohexylphenol, heptylphenol, diisobutylphenol (i.e., isooctylphenol), n-decylphenol, cetylphenol, oleylphenol, n-octadecylphenol, Wax-alkylated alphanaphthol, wax-alkyla'ted phenol, and polyisobutene-substituted phenol in which the polyisobutene substituent contains from about 12 to about 96 carbon atoms. The alkylphenol may also contain substituent groups such as, e.g., chloro, fluoro, nitro, alkoxy, sulfide, nitroso, etc. A particular preference is expressed for para-tertiary amylphenol. Also useful are alkylated polyhydric phenols such as alkylated resorcinols, alkylated catechols, alkylated pyrogallols, and their substitution products. Thus, n-octyl resorcinol, lauryl catechol, or cetyl pyrogallol may be used as the alkylphenol.

The following examples are presented to illustrate specific modes of preparing Component B. The acid number reported is determined according to ASTM Procedure D974-55T using the specified end point indicator.

Example 8 1900 parts (11.6 equivalents) of para-tertiary amylphenol is introduced into a reaction vessel and heated to 93 C. 440 parts (3.1 moles) of phosphorus pentoxide is then added over a period of 1 hour at 93-99 C. The whole is then heated to 154 C. over a hour period and maintained at that temperature for an additional 5 hours. Thereupon, the whole is allowed to cool to 93 C. and 585 parts of isobutanol solvent is added thereto. The product, an 80% solution of the desired mixed phosphate esters in iso'butanol shows the following analyses.

Phosphorus, percent 6.61 Acid number 1 120 1 Bromphenol blue indicator.

Example 9 1230 parts (7.5 equivalents) of para-tertiary amylphenol is introduced into a reaction vessel and heated to 99 C. over a period of 8 hours. The temperature is then elevated to 111 C. and 355 parts (2.5 moles) of phosphorus pentoxide is added over a period of 0.66 hour at 110l57 C. The whole is stirred thoroughly for an additional 5 hours at 150159 C. The mixture of phosphate esters thus obtained shows the following analyses.

Phosphorus, percent 9.61 Acid number 1 148 1 Bromphen'ol blue indicator.

Example 10 7,360 grams (16 equivalents) of mono-(polyisobutenesubstituted) phenol in which the polyisobutene substituent contains an average of 22 carbon atoms is introduced into a reaction vessel and heated to 88 C. Then 568 grams (4.0 moles) of phosphorus pentoxide is added over a period of 0.1 hour at 8811l C. The whole is then heated to 155 C. and maintained at 155 160 C. for 5 hours to complete the reaction. The product, a brown viscous liquid, shows the following analyses.

Phosphorus, percent Acid number 1 Bromphenol blue indicator.

Example 11 1,026 parts (2.22 equivalents based on the hydroxyl value) of mono-(polyisobutene-substituted) phenol in which the polyisobutene substituent contains an average of 62 carbon atoms is introduced into a reaction vessel along with 376 parts of Xylene solvent. The whole is heated to 38 C. and 105 parts (0.74 mole) of phosphorus pentoxide is added over a period of 0.25 hour at 38 C. The whole is then heated to C. and maintainedat that temperature for 3 hours. The crude productis filtered to insure perfect clarity. The filtrate, a 75% solution of the desired phosphate esters in xylene solvent, shows the following analyses.

Phosphorus, percent Acid number 1 Thymolphthalein indicator.

Example 12 881 grams of mixed cresols is introduced into a reaction vessel and 344 grams of phosphorus pentoxide is added thereto over a period of 3.5 hours (a 3:1 ratio of phenolic hydroxylzphosphours pentoxide). An exothermic reaction carries the temperature from 26 C. to 61 C. The whole is then stirred for 1 hour at77 C. and filtered to remove a few small particles. The filtrate shows the following analyses.

Phosphorus, percent 12.1 Acid number 1 210 1 Methyl red indicator.

Example 13 660 grams (3 equivalents) of nonylphenol is introduced into a reaction vessel and 142 grams (1 mole) of phosphorus pentoxide is added thereto over a period of 1 hour. An exothermic reaction carries the temperature from 43 C. to 70 C. The whole is then stirred an additional 2 hours at 70 C. and filtered for purposes of purification. The phosphate esters thus obtained show the following analyses.

Phosphorus, percent 5.34 Acid number 1 174 1 Phenolphthalein indicator,

exposure to air or by means of a baking procedure. A 1

dried film thickness of the corrosion-proofing composition of this invention or of a known coating composition containing the same ranging from about 0.01 mil to about 4 mils, preferably 0.02-2 mils, is usually required to provide adeqaute protection for the metal article. Coatings heavier than 4 mils can be used, if desired, for applications where such coatings provide additional wanted benets. rosion-proofing composition of this invention with a pigment such as titanium dioxide, chrome green, aluminum powder, carbon black, iron oxide, or zinc chromate. In

some instances, it is also desirable to include conventional improving agents such as pigment extenders, anti-skinning agents, driers, gloss agents, color stabilizers, etc.

As indicated earlier, the corrosion-proofing composi- In some instances, it is desirable to admix the cort tions of this invention comprise from about 0.05 to about 20 parts by weight of Component A per part of Component B. When Components A and B are mixed there is a slight, but perceptible, rise in temperature. Analytical evidence indicates that upon mixing, at least a portion of the hexavalent chromium in Component A is reduced to trivalent chromium. This phenomenon is believed to be at least partially responsible for the excellent corrosion-proofing characteristics of the compositions of this invention. In any event, Components A and B may be pre-mixed and packaged, mixed just prior to use, or lended with a known siccative organic composition prior to packaging or just prior to application to a metal article.

A number of laboratory tests were carried out to determine the utility of the hereindescribed corrosion-proofing compositions. Unless otherwise indicated, all parts and percentages are by weight.

Example 14 A 4-inch x 8-inch panel of 20 gauge SAE 1020 coldrolled steel was brush-coated with a primer made according to Federal Specification TIP-00615b from 4,590 parts of basic lead silica-chromate, 22.5 parts of castor wax, 270 parts of pigment grade Fe O 1,560 parts of linseed oil, 620 parts of an alkyd resin, 665 parts of mineral spirits, and 11.25 parts each of a solution of cobalt naphthenate in mineral spirits having a cobalt content of 6 percent and a solution of lead naphthenate in mineral spirits having a lead content of 24 percent.

A similar steel panel was brush-coated with a primer like that described above, except that 140 parts of the alkyd resin and 60 parts of the mineral spirits were replaced with 200 parts of a corrosion-proofing composition of this invention consisting of 14 percent of the product of Example 1, 47 percent of the product of Example, 8, and 39 percent of aromatic petroleum spirits.

The primed panels, labeled E and F, respectively, were scribed with a sharp steel instrument to yield a deep score beginning one inch from the top of the panel and ending one inch from the bottom thereof. l' he scribed panles were subjected to the Salt Fog Corrosion test described in ASTM Procedure B117-57T. In this test a mist or fog of percent aqueous sodium chloride is maintained in contact with the panels for a predetermined time (in this case 288 hours) at 95i-2 F. After the panels had been so exposed, they were removed from the Salt Fog chamber, washed with tap water to remove salt deposits and any loosened paint film, and inspected to determine the percent of the original paint film which was still intact (i.e., tightly adhered and free from blistering and flaking). The test results are recorded in Table I.

TABLE I.SALT FOG CORROSION TEST, 288 HOURS Percent of film intact E (control) 65 F (of the invention) 85 It will be noted that a corrosion-proofing composition of this invention substantially improved the adhesion of a known primer to a ferrous metal article.

Primed steel panel:

Example 15 TABLE II.WATER IMERSION TEST, 16 HOURS AT 160 F.

Primed steel panel: Condition of coating E (control) Heavily blistered. F (of the invention) Intact, no blistering.

It will be noted that the coating prepared in accordance 10 with the present invention showed perfect adhesion to the metal substrate.

' Example 16 An experiment like that described in Example 14 was carried out, except that in preparing the coating composition of the invention, 140 parts of alkyd resin and 60 parts of mineral spirits of such composition were replaced with 200 parts of a corrosion-proofing composition of the invention consisting of 15 percent of the product of Example 1, 37.5 percent of the product of Example 10, and 47.5 percent of mineral spirits. The control panel and panel of the invention were labeled G and H, respectively. The test results are set forth in Table III.

TABLE III.'SALT FOG CORROSION TEST, 288 HOURS Primed steel panel: Percent of film intact G (control) 65 H (of the invention) It will be noted that again a corrosion-proofing composition of this invention substantially improved the adhesion of a known primer to a ferrous metal article.

Example 17 Two panels, G and H, were prepared in the manner set forth in Example 16 and then subjected to the Water Immersion test described in Example 15. The test results are given in Table IV.

TABLE IV.WATER IMMERSION TEST, 16 HOURS AT 160 F.

Primed steel panel: Condition of coating G (control) Densely covered with small blisters. H (of the invention) Intact, no blisters or flaking.

It will be noted that the coating prepared in accordance with the present invention adhered perfectly to the metal substrate.

Example 18 Two uncoate-d steel panels like those described in Example 14 were prerusted by exposing them outdoors for two months. One such panel was brush-coated with a paint made according to Federal Specification TTP-86bI from 6200 parts of red lea-d, 16 parts of aluminum stearate, 872 parts of raw linseed oil, 304 parts of bodied linseed oil, 560 parts of mineral spirits, and 48 parts of a solution of cobalt naphthenate in mineral spirits having a cobalt content of 1 percent.

The other panel was brush-coated with a paint similar to that described above except that 120 parts each of the raw linseed oil and mineral spirits were replaced with 240 parts of a corrosion-proofing composition of the invention consisting of 90 parts of the product of Example 7, 30 parts of the product of Example 9, and parts of mineral spirits.

The coated panels, labeled J and K, respectively, were then scribed and subjected to the Salt Fog Corrosion test described in Example 14, except that the test duration was 120 hours rather than 288 hours. The test results are set forth in Table V.

TABLE V.SALT FOG CORROSION TEST, 1'20 HOURS Pre-rusted, coated panel: Percent of film intact I (control) 5 K (of the invention) 90 The above results show that a coating composition prepared in accordance with this invention tightly adheres to a rusted metal surface, whereas a similar composition not containing the corrosion-proofing composition of this invention is almost completely removed under the severe exposure conditions of the Salt Fog Corrosion test.

In addition to their utility as protective coating materials for ferrous metals and galvanized ferrous metals,

l l the corrosion-proofing compositions of this invention are also useful in protecting non-ferrous metals and alloys thereof such as aluminum, magnesium, cadmium, copper, brass, bronze, white metals, etc., against corrosion. They are also useful in protecting plated metal surfaces such as copper-plated, nickel-plated, and cadmium-plated ferrous metal articles against corrosion. They are also useful as protective coating materials on phosphated metal surfaces and on chromated aluminum or chromated zinc surfaces, i.e., aluminum or Zinc surfaces which have been treated with an aqueous solution of chromic acid or a derivative thereof such as a metal chromate or dichromate. Excellent results are obtained when the corrosion-proofing compositions of the present invention are applied to a metal article which has been phosphated by means of a novel aqueous phosphating solution containing as essential ingredients zinc ion, phosphate ion, nitrate ion, and a cation selected from the group consisting of lithium, beryllium, magnesium, calcium, strontium, cadmium, and barium. Such phosphating solutions, which provide a dense, adherent, micro-crystalline or amorphous phosphate coating upon a metal surface, are described in detail in co-pending US. application, Serial No. 373,449, filed August 10, 1953, now Patent No. 3,090,709. It is intended that the entire disclosure of Serial No. 373,449 be incorporated herein by reference.

What is claimed is:

1. A liquid corrosion-proofing composition adapted to form a protective coating on metal articles which oomprises the combination of:

(A) the product obtained by mixing one mole of at least one aliphatic amine containing at least about 6 carbon atoms with from about 0.25 to about 2 moles of aqueous chromic acid and heating the mixture to remove substantially all water present, and

(B) a mixture of phosphate esters prepared by the process which comprises the reaction of:

(a) one mode of a phosphorus-containing reagent selected from the group consisting of phosphorus pentoxide and phosphoric acids with (b) from about 1 to about 10 moles of an alkylphenol at a temperature of at ieast about 40 C.

2. A corrosion-proofing composition in accordance 4. A corrosion-proofing composition in accordance with claim 1 wherein the aliphatic amine reactant of A is a mixture of C to C 'tert'iary-alkyl primary amines.

5. A corrosion-proofing composition in accordance with claim 1 wherein the aliphatic amine reactant of A is Z-ethylhexylamine.

6. A corrosion-proofing composition in accordance with claim 1 wherein the phosphorus-containing reagent of B is phosphorus pent-oxide.

7. A corrosion-proofing composition in accordance with claim 1 wherein the alkylphenol of B is paratertiary amylphenol.

S. A corrosion-proofing composition in accordance with claim 1 wherein the a'lky'lphenol of B is a polyisobutene-substituted phenol in which the polyisobutene substitutent contains from about 12 to about 96 carbon atoms.

9. A method for inhibiting the corrosion of a metal article which comprises applying thereto a film comprising the composition of claim 1. p

10. A method in accordance with claim 9 wherein said film comprises a major proportion of a sicc ative organic coating composition and a minor proportion of the composition of claim 1.

References Cited by the Examiner UNITED STATES PATENTS 3,133,837 5/1964 Higgins 148-6.l5

ALFRED L. LEAVITT, Primary Examiner. R. S. KENDALL, Assistant Examiner.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,287,178 November 22, 1966 Robert G. Wurstner It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 1, line 31, for "pressure" read presence line 37, for "exculding" read excluding column 4, line 41, strike out "for"; column 8, line 27, for "phosphours" read phosphorus line 58, for "trupentine" read turpentine line 65, for "adeqaute" read adequate column 9, line 41, for "panles" read panels column 11, line 38, for "mode" read mole Signed and sealed this 12th day of September 1967.

(SEAL) Attest: ERNEST W. SWIDER EDWARD J. BRENNER Attesting Officer Commissioner of Patents 

1. A LIQUID CORROSION-PROOFING COMPOSITION ADAPTED TO FORM A PROTECTIVE COATING ON METAL ARTICLES WHICH COMPRISES THE COMBINATION OF: (A) THE PRODUCT OBTAINED BY MIXING ONE MOLE OF AT LEAST ONE ALIPHATIC AMINE CONTAINING AT LEAST ABOUT 6 CARBON ATOMS WITH FROM ABOUT 0.25 TO ABOUT 2 MOLES OF AQUEOUS CHROMIC ACID AND HEATING THE MIXTURE TO REMOVE SUBSTANTIALLY ALL WATER PRESENT, AND (B) A MIXTURE OF PHOSPHATE ESTERS PREPARED BY THE PROCESS WHICH COMPRISES THE REACTION OF: (A) ONE MODE OF A PHOSPHORUS-CONTAINING REAGENT SELECTED FROM THE GROUP CONSISTING OF PHOSPHORUS PENTOXIDE AND PHOSPHORIC ACIDS WITH (B) FROM ABOUT 1 TO ABOUT 10 MOLES OF AN ALKYLPHENOL AT A TEMPERATURE OF AT LEAST ABOUT 40*C. 